Figure 15. Receptor-Catalyzed GTPγS Exchange.
A fluorescence spectrum obtained for 200 nM Gt activated by 100 nM purified rhodopsin in the presence of 10 μM GTPγS. Excitation is at 280 nm, and emission is at 340 nm. The baseline is collected from 0–10 minutes (fluorescence in the absence of GTPγS). Upon addition 10 μM GTPγS, the fluorescence signal increases until Gt is maximally activated (~30 minutes).